JP3861846B2 - Rotating linear converter and fuel injection pump - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a rotary linear converter and a fuel injection pump that convert rotation into a reciprocating motion in a linear direction.
[0002]
[Prior art]
An example of converting the rotation into a reciprocating motion in the linear direction will be described with reference to FIG.
5 is used for a fuel injection pump. An eccentric cam J2 that rotates eccentrically with respect to the rotational axis of the camshaft J1, and a cylindrical slide bearing J3 (bushing) around the eccentric cam J2. ) And a plunger J6 that is slidably supported in a direction perpendicular to the axis of rotation by the cylinder head J5 and pressed against the cam ring J4. It has. The plunger plane J8 formed at the end of the plunger J6 is in sliding contact with the cam ring plane J7 formed on the outer surface in the radial direction of the cam ring J4, and the rotation of the cam ring J4 is restricted (Patent Document 1, Patent Document). Reference 2: Patent Document 1 and Patent Document 2 are not known techniques).
[0003]
[Patent Document 1]
Japanese Patent Application 2001-355821
[Patent Document 2]
Japanese Patent Application No. 2002-347438
[0004]
[Problems to be solved by the invention]
On the other hand, the cam ring J4 is covered with a housing, and a cam chamber filled with fuel is formed between the cam ring J4 and the housing, and the sliding contact surface of the cam ring J4 and the plunger J6 is lubricated by the fuel in the cam chamber. .
If water enters the sliding contact surfaces of the cam ring J4 and the plunger J6, the sliding contact surfaces of the cam ring J4 and the plunger J6 become poorly lubricated, and a large thrust resistance such as seizure occurs on the sliding contact surfaces of the cam ring J4 and the plunger J6. .
[0005]
Here, the eccentric cam J2 is rotationally driven by the output of the engine via the camshaft J1, so that a large rotational torque is applied to the eccentric cam J2.
Therefore, if seizure or the like occurs on the sliding contact surface between the cam ring J4 and the plunger J6, a strong rotational torque is transmitted to the plunger J6, and the plunger J6 is damaged.
[0006]
When the plunger J6 is broken, the broken piece is pushed into the gap between the cam ring J4 and the housing, which may damage the housing (usually made of aluminum). In order to prevent damage to the housing, the gap between the cam ring J4 and the housing must be increased, and the physique of the fuel injection pump that is required to be reduced in size is greatly increased.
Even if the housing is not damaged, if a large thrust resistance occurs, such as seizure on the sliding contact surface between the cam ring J4 and the plunger J6, a strong rotational torque is transmitted to the plunger J6. The cylinder head J5, the cam ring J4, etc. that support the cylinder will be deformed and the repair cost will be high.
[0007]
OBJECT OF THE INVENTION
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a rotating linear conversion device capable of minimizing damage when a large thrust resistance is generated on the sliding contact surfaces of the cam ring and the plunger. To provide a fuel injection pump.
[0008]
[Means for Solving the Problems]
[Means of Claim 1]
According to a first aspect of the present invention, there is provided a rotating linear converter having a cam ring provided with a safety device that breaks when a predetermined load or more is applied in the rotational direction.
By providing in this way, when a large thrust resistance is generated due to seizure of the sliding surface between the cam ring and the plunger, the cam ring safety device is broken. Then, since the cam ring is opened and the inner diameter of the cam ring is increased, the eccentric cam rotates idly on the inner periphery of the cam ring. As a result, the rotational torque of the eccentric cam is not transmitted to the cam ring, and a large load is prevented from being applied to the plunger.
That is, when a large thrust resistance is generated on the sliding contact surface between the cam ring and the plunger, the damaged portion can be limited only to the cam ring, and as a result, the damage can be minimized.
According to the first aspect of the present invention, a safety device is provided in a portion that is not a sliding contact surface between the cam ring and the plunger, and a portion to which a large stress is applied when the sliding resistance between the cam ring and the plunger is increased. .
By providing in this way, when a large thrust resistance is generated on the sliding contact surface between the cam ring and the plunger, the safety device breaks in a state where the load applied in the rotation direction of the cam ring is relatively small.
For this reason, damage given to other than the cam ring can be made extremely small.
[0009]
[Means of claim 2]
According to a second aspect of the present invention, there is provided a fuel injection pump that employs the rotation linear conversion device employing the means of claim 1 as means for reciprocally driving a plunger by rotation of an eccentric cam that is driven to rotate by an engine. .
[0010]
That is, when water or the like enters the sliding surface of the cam ring and the plunger and the sliding surface becomes poorly lubricated, seizure occurs on the sliding surface of the cam ring and the plunger, and a large thrust resistance occurs on the sliding surface. A heavy load from the engine is applied to the cam ring, and the cam ring safety device breaks.
Then, since the cam ring is opened and the inner diameter of the cam ring is increased, the eccentric cam rotates idly on the inner periphery of the cam ring. As a result, the rotational torque of the eccentric cam is not transmitted to the cam ring, and a large load is prevented from being applied to the plunger.
That is, when a large thrust resistance is generated on the sliding contact surface between the cam ring and the plunger, the damaged portion can be limited only to the cam ring, and as a result, the damage can be minimized.
According to a second aspect of the present invention, a safety device is provided in a portion which is not a sliding contact surface between the cam ring and the plunger and where a large stress is applied when the sliding resistance between the cam ring and the plunger is increased. .
By providing in this way, when a large thrust resistance is generated on the sliding contact surface between the cam ring and the plunger, the safety device breaks in a state where the load applied in the rotation direction of the cam ring is relatively small.
For this reason, damage given to other than the cam ring can be made extremely small.
[0011]
Specifically, since the plunger is prevented from being damaged, the plunger is damaged, and the fragments are pushed into the gap between the cam ring and the housing, so that the housing is not damaged and the fuel does not leak to the outside. For this reason, it is not necessary to increase the gap between the cam ring and the housing, and it is not necessary to increase the size of the fuel injection pump.
Further, the breakage occurs only in the cam ring, and since the load applied to the plunger, the cylinder head that supports the plunger, and the cam ring is small, the repair cost can be kept low.
[0013]
[Means of claim 3 ]
The safety device of the means of claim 3 is a notch groove formed in at least one of the outer peripheral surface or inner peripheral surface of the cam ring.
The cutout groove does not limit the shape such as V-shape, U-shape, and C-shape. Further, the length of the cutout groove may be formed from end to end in the rotation axis direction of the cam ring, or may be formed only in part.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described using examples and modifications.
〔Example〕
An embodiment will be described with reference to FIGS.
First, the configuration of the fuel injection pump will be described. 1 is a cross-sectional view of the fuel injection pump viewed from the axial direction, and FIG. 2 is a cross-sectional view of the fuel injection pump along the axial direction.
[0015]
The fuel injection pump 1 sends fuel compressed to a high pressure to the common rail of the fuel injection device. The fuel injection pump 1 is a feed pump 2 (disclosed in a state of 90 ° expansion in FIG. 2), a regulator valve 3, and a fuel metering valve. 4 (SCV), constituted by a high-pressure pump 5.
The housing of the fuel injection pump 1 includes a housing body 6, a housing cover 7 and a cylinder head 8. The housing body 6 and the housing cover 7 are made of aluminum, and the cylinder head 8 is made of iron.
[0016]
The feed pump 2 is a trochoid pump that is rotationally driven by a camshaft 11. When this trochoid pump is driven, the fuel sucked from the fuel inlet 10 is supplied to the high-pressure pump 5 through the fuel metering valve 4. is there.
The camshaft 11 is rotationally driven by an engine crankshaft or the like.
[0017]
The regulator valve 3 is disposed in a fuel passage that connects the discharge side and the supply side of the feed pump 2 and opens when the discharge pressure of the feed pump 2 rises to a predetermined pressure, and the discharge pressure of the feed pump 2 reaches a predetermined pressure. Is not exceeded.
[0018]
The fuel metering valve 4 controls the amount of fuel supplied to the high-pressure pump 5 by energization control of the coil by an ECU (abbreviation of engine control unit) (not shown).
The fuel metering valve 4 controls the fuel supply amount to the high-pressure pump 5, whereby the fuel pressure of the common rail is controlled.
[0019]
The high-pressure pump 5 compresses the fuel supplied from the fuel metering valve 4 to a high pressure and supplies it to the common rail, and converts the rotation transmitted from the engine into a linear reciprocating motion of the plunger 12. , One or a plurality (two in this embodiment) of the plunger pump unit 14 that performs suction and compression / discharge of the fuel by reciprocating movement of the plunger 12, and a suction valve that supplies the fuel to the pressurizing chamber 15 of the plunger pump unit 14 16. A discharge valve 17 is provided for discharging the fuel compressed in the pressurizing chamber 15 toward the common rail.
[0020]
The rotating linear conversion device 13 is provided inside a cam chamber 18 formed inside the housing. The rotating linear conversion device 13 is eccentrically rotated with an eccentric cam 19, a cam ring 21 mounted around the eccentric cam 19, and pressed against the cam ring 21. And a reciprocating plunger 12.
Here, the cam chamber 18 is supplied with fuel from the feed pump 2 through the fuel passage 22 in which the throttle 22a is formed, and the cam chamber 18 is filled with fuel. Excess fuel in the cam chamber 18 is discharged from the fuel outlet 23 and returned to a fuel tank (not shown).
The eccentric cam 19 is a cylindrical body provided integrally with or coupled to the camshaft 11 that is rotationally driven by the rotational output of the engine, and is eccentric with respect to the rotation center of the camshaft 11 when the camshaft 11 rotates. Rotate.
[0021]
The cam ring 21 is slidably supported via a cylindrical slide bearing 24 (bush) mounted around the eccentric cam 19, and has a through hole 21a through which the eccentric cam 19 and the slide bearing 24 are inserted. Prepare.
On the outer surface of the cam ring 21, a cam ring plane 21 b (sliding contact surface) is provided at a portion that comes into sliding contact with the plunger 12. In this embodiment, two plungers 12 are arranged opposite to each other with the cam ring 21 interposed therebetween. For this reason, on the outer surface of the cam ring 21, a cam ring plane 21 b slidably in contact with one plunger 12 and a cam ring plane 21 b slidably in contact with the other plunger 12 are formed at positions facing each other.
[0022]
Here, an umbrella portion 12a (tappet portion) is integrally formed at the end portion (end portion on the rotation center side) of the plunger 12, and a cam ring is formed on the inner surface (rotation center side surface) of the umbrella portion 12a. A plunger flat surface 12b (sliding contact surface) that is in sliding contact with the flat surface 21b is formed.
A spring 25 is disposed between the umbrella portion 12a and the cylinder head 8, and the plunger plane 12b is always pressed toward the cam ring plane 21b.
Due to the urging force of the spring 25 and the pressure of the fuel received by the plunger 12 from the pressurizing chamber 15, the rotation of the cam ring 21 itself is regulated and rotates eccentrically.
[0023]
On the other hand, the plunger pump unit 14 includes a plunger 12 that is slidably supported in a cylinder 8a formed in the cylinder head 8, and reciprocates in the cylinder 8a, thereby The pressurizing chamber 15 surrounded by the cylinder 8a repeats expansion and contraction.
When the plunger 12 descends (moves toward the center of rotation), the volume of the pressurizing chamber 15 expands, the pressure in the pressurizing chamber 15 decreases, the discharge valve 17 closes, and the suction valve 16 opens. The fuel pumped by the feed pump 2 and metered by the fuel metering valve 4 is sucked into the pressurizing chamber 15.
Conversely, when the plunger 12 is raised (moved to a side different from the rotation center), the volume of the pressurizing chamber 15 is reduced, the fuel in the pressurizing chamber 15 is pressurized, and the intake valve 16 is closed. . When the pressure of the fuel pressurized in the pressurizing chamber 15 reaches a predetermined pressure, the discharge valve 17 is opened, and the high-pressure fuel pressurized in the pressurizing chamber 15 is discharged toward the common rail.
[0024]
Next, the operation of the rotating linear converter 13 will be described with reference to FIG.
Here, the time when the plunger 12 descends toward the rotation center and sucks fuel into the pressurizing chamber 15 is referred to as a suction process, and conversely, when the plunger 12 rises toward the suction valve and pressurizes the fuel in the pressurizing chamber 15. Is a pressurizing step.
In FIG. 3, the upper and lower two plungers 12 are opposed to each other with the cam ring 21 interposed therebetween as described above, and are driven with a 180 ° phase shift. That is, when one plunger 12 is in the suction process, the other plunger 12 is in the pressurizing process.
[0025]
As shown at the left end of FIG. 3, when the rotation center of the eccentric cam 19 is directly below the rotation center of the camshaft 11, the upper plunger 12 is at the bottom dead center and the lower plunger 12 is at the top dead center. It is in. The rotation angle θ at this time is 0 °.
When the camshaft 11 rotates counterclockwise in FIG. 3, the eccentric cam 19 and the cam ring 21 rotate eccentrically as the camshaft 11 rotates.
Then, the upper plunger 12 that comes into contact with the upper cam ring plane 21b of the cam ring 21 starts to move from the bottom dead center to the top dead center. When the rotation angle θ of the camshaft 11 is in the range of 0 ° <θ <180 °, the upper plunger 12 is in a pressurizing process and strokes in the cylinder 8a from the bottom dead center to the top dead center.
On the other hand, when the rotation angle θ of the camshaft 11 is in the range of 0 ° <θ <180 °, the lower plunger 12 enters a suction process and strokes in the cylinder 8a from the top dead center to the bottom dead center.
[0026]
When the upper plunger 12 is in the pressurizing step, a large force is applied to the upper plunger 12 in the cam ring direction due to the biasing force of the spring 25 and the pressure of the fuel pressurized in the pressurizing chamber 15.
On the other hand, when the lower plunger 12 is in the suction process, a large force is applied to the lower plunger 12 in the cam ring direction by the urging force of the spring 25.
That is, the biasing force in the cam ring direction by the plunger 12 during the pressurizing process is larger than the biasing force in the cam ring direction by the plunger 12 during the suction process.
[0027]
Here, the two cam ring planes 21b formed on the cam ring 21 are formed non-parallel, and the two plungers 12 have parallel (including concentric) central axes in the stroke direction. Therefore, when the force applied to the two plungers 12 is large or small, the plunger plane 12b to which a larger force is applied and the cam ring plane 21b come into surface contact.
Therefore, when the upper plunger 12 is in the pressurizing step, the upper plunger plane 12b and the upper cam ring plane 21b are in surface contact with each other, and there is a predetermined gap between the lower plunger plane 12b and the lower cam ring plane 21b. The fuel filled in the cam chamber 18 flows into the gap between the lower plunger plane 12b and the lower cam ring plane 21b.
[0028]
As shown in FIG. 3, when the rotation angle θ of the camshaft 11 becomes θ = 180 °, the upper plunger 12 reaches the top dead center, and the lower plunger 12 reaches the bottom dead center. Therefore, the upper plunger 12 ends the pressurizing process, and the lower plunger 12 ends the inhaling process.
[0029]
When the rotation angle θ of the camshaft 11 is 180 ° <θ, the upper plunger 12 shifts to the suction step and the lower plunger 12 moves to the pressurization step, contrary to the above-described 0 ° <θ <180 °. Transition.
Therefore, the lower plunger plane 12b and the lower cam ring plane 21b that perform the pressurizing step are in surface contact with each other, and a predetermined angle is formed between the upper plunger plane 12b and the upper cam ring plane 21b. The fuel filled in the cam chamber 18 flows into the gap between the plunger plane 12b and the upper cam ring plane 21b.
When the rotation angle θ of the camshaft 11 becomes θ = 360 °, the camshaft 11 enters an initial state (θ = 0 °) and repeats the above operation.
[0030]
[Features of Examples]
As described above, during the suction process, a gap is formed on the sliding contact surface between the plunger plane 12b and the cam ring plane 21b, and the fuel filled in the cam chamber 18 flows into the gap.
However, as described in the section “Problems to be Solved by the Invention”, when water enters the sliding surface between the cam ring plane 21b and the plunger plane 12b for some reason, the sliding surface becomes poorly lubricated, Seizure may occur on the sliding surface.
The eccentric cam 19 that rotates the cam ring 21 eccentrically is driven by the output of the engine. Therefore, when seizure occurs on the sliding contact surface, a strong rotational torque of the engine is transmitted to the plunger 12 through the seized portion. 12 will be damaged. When the plunger 12 is broken, the broken piece may be pushed into the gap between the cam ring 21 and the housing body 6 that covers the periphery of the cam ring 21, and the housing body 6 may be broken.
[0031]
Therefore, in the cam ring 21 of this embodiment, as shown in FIG. 1, a load of a predetermined amount or more in the rotation direction (a load that is a little larger than the load applied during normal operation: at least the housing body 6 that covers the periphery of the cam ring 21 is provided. A safety device 26 is provided that breaks when a load less than the breaking strength is applied.
The safety device 26 is a weak structural portion provided so as to be intentionally broken when a large rotational load is applied. The safety device 26 shown in this embodiment has a cross section formed on the outer peripheral surface of the cam ring 21. It is a V-shaped cutout groove. This notch groove is formed from end to end in the rotational axis direction, but may be formed only in part.
[0032]
The safety device 26 of this embodiment is a portion that is not a sliding contact surface between the cam ring 21 and the plunger 12, and when the sliding resistance between the cam ring 21 and the plunger 12 increases (when seizure or the like occurs), the stretching stress is increased. It is provided in the part which greatly adds.
Further, in this embodiment, two safety devices 26 are provided at the opposite positions of the cam ring 21 as shown in FIG. 1 so that the safety device 26 is broken by the stretching stress even if one of the two plungers 12 is seized. Yes.
[0033]
With reference to FIG. 4, the operation when seizure occurs on the sliding contact surface between the cam ring plane 21b and the plunger plane 12b will be described.
As described above, at the time of the plunger 12 intake process, a gap is formed between the cam ring plane 21b and the plunger plane 12b, and fuel flows in. When water enters the gap for some reason and the plunger 12 shifts to the pressurizing step, the sliding contact surface becomes poorly lubricated and seizure occurs on the sliding contact surface.
Since the eccentric cam 19 is driven by the output of the engine, even if seizure occurs during the pressurizing process (see the second diagram from the left in FIG. 4), the eccentric cam 19 rotates eccentrically. That is, the eccentric cam 19 rotates even if the portion indicated by the arrow A in FIG. Then, “a force that is greater than that in the normal state” is applied to the portion indicated by the symbol B in FIG. 4 of the cam ring 21, and “a force that is greater than that in the normal state is applied to the portion indicated by the symbol C in FIG. "Is added.
[0034]
4 is applied to the portion indicated by the symbol B in FIG. 4, the safety device 26 provided on the cam ring 21 is broken. Then, since the cam ring 21 is opened and the inner diameter of the cam ring 21 is increased, the eccentric cam 19 rotates idly on the inner periphery of the cam ring 21.
As a result, the rotational torque of the eccentric cam 19 is not transmitted to the cam ring 21, and there is no problem that a large load is applied to the plunger 12.
[0035]
[Effects of Examples]
As described above, water or the like enters the sliding contact surface between the cam ring 21 and the plunger 12 (specifically, the sliding contact surface between the cam ring plane 21b and the plunger plane 12b) and the sliding contact surface becomes poorly lubricated. When seizure or the like is generated on the surface and a large thrust resistance is generated on the sliding contact surface, a strong rotational torque received from the engine is applied to the cam ring 21, the safety device 26 of the cam ring 21 is broken, the cam ring 21 is opened, and the cam ring 21 is opened. The eccentric cam 19 runs idle on the inner circumference of the. As a result, the rotational torque of the eccentric cam 19 is not transmitted to the cam ring 21 and a large load is prevented from being applied to the plunger 12 and the like.
For this reason, the damage which arises in the fuel injection pump 1 can be suppressed to the minimum.
[0036]
Specifically, damage to the plunger 12 is prevented. For this reason, the plunger 12 is damaged, and the fragments are pushed into the gap between the cam ring 21 and the housing main body 6 covering the cam ring 21, so that the housing main body 6 is not damaged and the fuel does not leak outside. For this reason, it is not necessary to increase the gap between the cam ring 21 and the housing body 6, and the physique of the fuel injection pump 1 need not be increased.
Further, only the cam ring 21 is broken, and the load applied to the plunger 12, the cylinder head 8 supporting the plunger 12, and the cam ring 21 is small, so that the repair cost can be kept low.
[0037]
Further, in this embodiment, since the safety device 26 is provided at a portion where the extension stress is greatly applied, when a large thrust resistance is generated on the sliding contact surface between the cam ring 21 and the plunger 12, a load applied in the rotation direction of the cam ring 21 is relatively large. The safety device 26 is broken in a small state. For this reason, the damage given to those other than the cam ring 21 can be made extremely small.
[0038]
[Modification]
In the above embodiment, the safety device 26 is provided as a V-shaped cutout groove. However, the safety device 26 may be provided by a cutout groove having another shape such as a U-shape or a C-shape. Moreover, although the example which formed the notch groove as the safety device 26 in the outer peripheral surface of the cam ring 21 was shown, you may form in the inner peripheral surface of the cam ring 21. FIG. Moreover, you may provide in both an outer peripheral surface and an internal peripheral surface.
[0039]
In the above embodiment, an example in which the safety device 26 is provided as a notch groove has been described. This thin portion may be formed from end to end in the rotational axis direction of the cam ring 21 or may be formed only in part.
Further, the safety device 26 may be provided by one or a plurality of through holes penetrating the outer peripheral surface and the inner peripheral surface of the cam ring 21.
[0040]
In the embodiment example above, the present invention is applied to the rotary linear converter 13 of the fuel injection pump 1, the present invention in addition to the rotational linear converter 13 for reciprocating the plunger 12 with Ekisenkamu 19 and cam ring 21 It may be applied.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a fuel injection pump as viewed from the axial direction (Example).
FIG. 2 is a cross-sectional view along the axial direction of the fuel injection pump (Example).
FIG. 3 is an operation explanatory diagram of the rotating linear conversion device (Example).
FIG. 4 is an operation explanatory diagram when seizure or the like occurs in the cam ring and the plunger (Example).
FIG. 5 is a cross-sectional view of the rotating linear conversion device as seen from the axial direction (conventional example).
[Explanation of symbols]
1 Fuel Injection Pump 5 High Pressure Pump 6 Housing Body (Housing Forming a Cam Chamber Around the Cam Ring)
DESCRIPTION OF SYMBOLS 11 Camshaft 12 Plunger 12b Plunger plane 13 Rotation linear converter 14 Plunger pump part 15 Pressurization chamber 16 Suction valve 18 Cam chamber 19 Excense cam 21 Cam ring 21b Cam ring plane 26 Safety device (notch groove)

Claims (3)

An eccentric cam that rotates and rotates eccentrically,
A cam ring that is slidably driven around the eccentric cam and rotated;
A plunger that is slidably supported in a direction perpendicular to the axis of rotation and is in contact with the cam ring in a state of being pressed against the cam ring;
In the rotary linear conversion device in which the plunger plane formed at the end portion of the plunger is in sliding contact with the cam ring plane formed on the outer surface in the radial direction of the cam ring, and the rotation of the cam ring is restricted.
The cam ring is provided with a safety device that breaks when a predetermined load or more is applied in the rotational direction ,
The safety device is provided in a portion which is not a sliding contact surface between the cam ring and the plunger, and a portion where a large stress is applied when the sliding resistance between the cam ring and the plunger is increased. Rotating linear converter. An eccentric cam that is rotationally driven by the rotational output of the engine and rotates eccentrically,
A cam ring that is slidably driven around the eccentric cam and rotated;
A plunger that is slidably supported in a direction perpendicular to the axis of rotation, is slidably contacted with the cam ring in a state of being pressed against the cam ring, and reciprocates to repeatedly expand and contract the fuel pressurizing chamber;
A housing forming a cam chamber around the cam ring,
Fuel is supplied into the cam chamber,
In the fuel injection pump in which rotation of the cam ring is restricted by sliding contact of a plunger plane formed at an end of the plunger with a cam ring plane formed on a radially outer surface of the cam ring.
The cam ring is provided with a safety device that breaks when a predetermined load or more is applied in the rotational direction ,
The safety device is provided in a portion which is not a sliding contact surface between the cam ring and the plunger, and a portion where a large stress is applied when the sliding resistance between the cam ring and the plunger is increased. Fuel injection pump. In the rotary linear converter or the fuel injection pump according to claim 1 or 2 ,
The rotary linear conversion device or the fuel injection pump, wherein the safety device is a notch groove formed in at least one of an outer peripheral surface or an inner peripheral surface of the cam ring.

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